KR20190038804A - Photocurable clear ink composition for inkjet printing - Google Patents

Abstract

There is a possibility that the clear ink tends to be microgelled by heat and the storage stability may be lowered. In addition, there is a problem that when the clear ink develops microgel over time, ink jet dischargeability is lowered. The present invention provides a clear ink composition for photocurable inkjet printing comprising a photopolymerizable compound, a photopolymerization initiator, and an inorganic filler having an average particle diameter of 1 to 200 nm in an amount of 0.05 to 5.0 mass% in the composition and a visible light transmittance of 30% or more.

Description

[0001] PHOTOCURABLE CLEAR INK COMPOSITION FOR INKJET PRINTING [0002]

The present invention relates to a clear ink composition for photocurable inkjet printing.

The composition disclosed in Patent Document 1 as a clear ink composition for photocurable inkjet printing is known. Such a composition does not contain a coloring pigment or extender pigment in a clear ink composition, but is a composition comprising only additives such as a curing component and a curing agent. Further, by printing a clear ink composition on the surface of the recording material by the color ink, a matte feeling can be given to the surface of the recording material.

Also, the clear ink composition for photocurable inkjet printing described in Patent Document 2 improves the smoothness of the recording medium by printing on a recording medium before printing the ink containing the metal powder without containing the metal powder or the colorant, It is possible to obtain an excellent gloss feeling and high quality.

Further, as described in Patent Document 3, it is known that the hardness of a cured product is increased by blending silica in a photopolymerizable inkjet colored ink to improve abrasion resistance and, as described in Patent Document 4, It is also known that zinc oxide, cerium oxide, and rutile-type titanium oxide, which are inorganic ultraviolet absorbers, are blended in an inkjet ink to effectively prevent discoloration by ultraviolet rays.

Japanese Patent Application Laid-Open No. 2015-057330 Japanese Patent Application Laid-Open No. 2014-172986 Japanese Patent Application Laid-Open No. 2015-081294 Japanese Patent Application Laid-Open No. 2011-219648

A clear ink composition for photocurable inkjet printing which is cured by light using an LED or the like as a light source is required to have high reactivity because it forms a cured coating film by radical polymerization of acrylate. On the other hand, if the reactivity is high, the reactivity due to heat tends to be high. At this time, the stability against heat is deteriorated and the storage stability of the ink deteriorates. For this reason, it is necessary to lower reactivity to heat while increasing reactivity to light.

In particular, clear ink tends to cause micro gelling due to heat, and there is a possibility that the storage stability is lowered. In addition, if a clear ink develops a microgel over time, there is a possibility that ink jet dischargeability is lowered.

As a clear ink composition for photocurable inkjet printing,

1. A clear ink composition for photocurable inkjet printing comprising a photopolymerizable compound, a photopolymerization initiator and 0.05 to 5.0 mass% of an inorganic filler having an average particle diameter of 1 to 200 nm in the composition and having a visible light transmittance of 30%

2. A clear ink composition for photocurable inkjet printing according to 1 wherein the inorganic filler is silica and / or aluminum oxide,

3. A clear ink composition for photocurable inkjet printing according to 1 or 2, which contains a pigment dispersant having an amino group and / or an acid group,

4. A clear ink composition for photocurable inkjet printing as described in any one of 1 to 3, wherein the photopolymerizable compound contains 50 to 75% by mass of the total amount of a monofunctional monomer having an amide group and benzyl acrylate in a clear ink composition for photocurable inkjet printing ,

5. The clear ink composition for photocurable inkjet printing according to any one of 1 to 4, wherein the monofunctional monomer having an amide group is N-vinylcaprolactam and / or acryloylmorpholine,

6. The clear ink composition for photocurable inkjet printing according to any one of 1 to 5, wherein the viscosity at 25 占 폚 is 10 mPa 占 퐏 or less

The above problems can be solved, and the present invention has been accomplished.

According to the present invention, since the clear ink composition for a photo-curable inkjet printing having a specific composition is excellent in curability in a thin film by ultraviolet rays, particularly ultraviolet rays using a light emitting diode (LED) as a light source, The storage stability of the ink composition could be improved.

Hereinafter, the clear ink composition for photocurable inkjet printing of the present invention (hereinafter also referred to as the ink composition of the present invention) will be described in detail.

The present invention provides a clear ink composition having a visible light transmittance of 30% or more by examining the average particle size and content of the pigment in a photocurable inkjet printing composition containing a photopolymerizable compound, a photopolymerization initiator and a pigment.

≪ Photopolymerizable compound >

The ink composition of the present invention may contain a monofunctional monomer or a polyfunctional monomer as a photopolymerizable compound.

(Monofunctional monomer)

Examples of the monofunctional monomer include alkyl (meth) acrylates such as methyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, methyl acrylate, butyl acrylate and 2-ethylhexyl acrylate, Alicyclic monofunctional monomers such as acrylate (meth) acrylate, phenoxyethyl (meth) acrylate, 4-t-butylcyclohexyl (meth) acrylate, dicyclopentenyl (meth) acrylate and cyclohexyl (Meth) acrylate such as benzyl methacrylate, alkoxyalkyl (meth) acrylate such as butoxyethyl methacrylate and butoxyethyl acrylate, triethylene glycol monobutyl ether, dipropylene glycol monomethyl ether (Meth) acrylic acid esters of polyalkylene glycol monoalkyl ethers such as hexaethylene glycol monophenyl ether, (Meth) acrylate, polyether (meth) acrylate, polyether (meth) acrylate, polyether (meth) acrylate, Acrylamide, N, N-dimethyl acrylamide, N, N-dimethyl methacrylamide, N, N-diethylacrylamide, N, N-diethyl N, N'-methylenebisacrylamide, N, N-dimethylaminopropylacrylamide, N, N-dimethylaminopropylmethacrylamide, diacetone acrylamide, (meth) acryloylmorpholine, N - monofunctional monomers having an amide group and / or an amino group such as vinylcaprolactam and N-vinylpyrrolidone, aminoethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) Dimethylaminopropyl (meth) acrylate And monofunctional monomers having an amino group such as a carboxyl group and a carboxyl group. These monofunctional monomers may be used alone or in combination of two or more.

The content of the monofunctional monomer in the clear ink composition is preferably not less than 40% by mass, more preferably not less than 50% by mass. The content of the monofunctional monomer in the clear ink composition is preferably 90% by mass or less, more preferably 80% by mass or less, and further preferably 75% by mass or less.

If the content of the monofunctional monomer is less than 40% by mass, the resulting cured coating film may have poor adhesion. On the other hand, when the content of the monofunctional monomer is more than 90% by mass, the resulting cured coating film may be deteriorated in tackiness and scratch resistance.

Among these monofunctional monomers, in order to improve the tackiness and curability of the resulting cured coating film, it is preferable that the composition contains 50 to 75% by mass of the total amount of the monofunctional monomer having amide group and benzyl acrylate.

As the monofunctional monomer having a preferable amide group, N-vinylcaprolactam and / or acryloylmorpholine can be exemplified.

<Multifunctional Monomers>

Examples of the polyfunctional monomer include an acrylated amine compound having two photopolymerizable functional groups and two amino groups in the molecule, vinyloxyethoxyethyl (meth) acrylate, 1,4-butanediol di (meth) acrylate, 1,6- Acrylate, diethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, ethylene glycol di (meth) acrylate, diethylene glycol di Acrylate, propylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, ethoxylated 1,6- (Meth) acrylate, ethoxylated neopentyl glycol di (meth) acrylate, ethoxylated bisphenol A di (meth) acrylate, cyclohexanedimethanol di (Meth) acrylate, alkoxylated hexanediol di (meth) acrylate, alkoxylated cyclohexanedimethanol di (meth) acrylate, alkoxylated di (meth) acrylate, tricyclodecanedimethanol di Acrylate, alkoxylated neopentyl glycol di (meth) acrylate, alkoxylated aliphatic di (meth) acrylate, trimethylolpropane tri (meth) acrylate, tris (2-hydroxyethyl (Meth) acrylates such as isocyanurate tri (meth) acrylate, pentaerythritol tri (meth) acrylate, ethoxylated trimethylol propane tri (meth) acrylate, propoxylated trimethylol propane tri (Meth) acrylate, pentaerythritol tetra (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, ethoxylated pentaerythritol Such as tall tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate and the like. One or more of these polyfunctional monomers may be used.

The content of the polyfunctional monomer in the clear ink composition should be not less than 15% by mass, preferably not less than 20% by mass. The content of the polyfunctional monomer in the clear ink composition is preferably 50% by mass or less, more preferably 35% by mass or less. When the content of the polyfunctional monomer is less than 15% by mass, the resulting cured coating film tends to have poor scratch resistance and tackiness. On the other hand, when the content of the polyfunctional monomer exceeds 50 mass%, the resulting cured coating film tends to have poor adhesion.

<Photopolymerization initiator>

As the photopolymerization initiator, any of an acylphosphine-based photopolymerization initiator and a triazine-based photopolymerization initiator may be employed.

The acylphosphine-based photopolymerization initiator is a photopolymerization initiator containing an acylphosphine group, and the triazine-based photopolymerization initiator is a photopolymerization initiator having a triazine structure. These photopolymerization initiators have light absorption properties over a wavelength range of 450 to 300 nm and are polymerized by polymerizing the clear ink composition upon irradiation with light of these specific wavelengths (UV-LED).

As the acylphosphine-based photopolymerization initiator, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2,6-dimethoxybenzoyldiphenylphosphine oxide, 2,6-dichlorobenzoyldiphenylphosphine oxide, 2,3,5 , 6-tetramethylbenzoyldiphenylphosphine oxide, 2,6-dimethylbenzoyldimethylphosphine oxide, 4-methylbenzoyldiphenylphosphine oxide, 4-ethylbenzoyldiphenylphosphine oxide, 4-isopropylbenzoyldiphenyl (2,4,6-trimethylbenzoyl) -phenylphosphine oxide, 2,4,6-trimethylbenzoylphenylphosphinic acid methyl ester, 2, 3-trimethylbenzoylphenylphosphinic acid methyl ester, (2,6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide, bis (2,6-dimethoxybenzoyl) -2,2,4-trimethylpentylphosphine oxide, 3,3-trimethyl-pentylphosphine oxide, and the like. Specifically, IRGACURE 819 (manufactured by BASF) as TPO (manufactured by Lamberti) and bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide as 2,4,6-trimethylbenzoyl-diphenyl- And the like.

As the triazine photopolymerization initiator, 2,4,6-trichloro-s-triazine, 2-phenyl-4,6-bis (trichloromethyl) -s- triazine, 2- (p- methoxyphenyl) (Trichloromethyl) -s-triazine, 2- (p-tolyl) -4,6-bis (trichloromethyl) (Trichloromethyl) -s-triazine, 2,4-bis (trichloromethyl) -6-styryl-s-triazine, 2- (naphtho- (Trichloromethyl) -s-triazine, 2,4-trichloromethyl- (2-methoxy-naphthol- Piperonyl) -6-triazine, 2,4-trichloromethyl (4'-methoxystyryl) -6-triazine and the like.

The content of the photopolymerization initiator is preferably 5.0% by mass or more, more preferably 6.0% by mass or more in the clear ink composition. The content of the photopolymerization initiator in the clear ink composition is preferably 15.0 mass% or less, more preferably 12.0 mass% or less. When the content of the photopolymerization initiator is less than 5.0% by mass, the clear ink composition may be liable to lower the UV-LED curability. In addition, by setting this range, it is difficult to cause yellowing in the cured coating film. On the other hand, when the content of the photopolymerization initiator is more than 15.0 mass%, the clear ink composition does not improve the effect of the curing property by further blending the photopolymerization initiator and tends to be excessively added.

The clear ink composition of the present embodiment is preferably blended with 5.0 to 15.0 mass% of an acylphosphine-based photopolymerization initiator, and other photopolymerization initiators may be used in combination within a range not deteriorating the performance. The photopolymerization initiator may be used alone or in combination of two or more. As the other photopolymerization initiator, a thioxanthone photopolymerization initiator, an? -Hydroxyketone photopolymerization initiator, or the like may be used in combination.

<An inorganic filler having an average particle diameter of 1 to 200 nm>

As the inorganic filler for use in the present invention having an average particle size of 1 to 200 nm, preferably an average particle size of 1 to 100 nm, an extender pigment is preferable, and silica, aluminum oxide and calcium carbonate are preferably used, Is silica and aluminum oxide. These inorganic fillers may be used alone or in combination of two or more.

These pigments are pulverized as necessary to give an average particle diameter of 1 to 200 nm, preferably 1 to 100 nm. The average particle diameter is a value measured by the following method. The average particle diameter was measured using Microtrac UPA-150 manufactured by Nikkiso Co., Ltd.

The inorganic filler having an average particle diameter of 1 to 200 nm is compounded in an amount of 0.05 to 5.0% by mass, preferably 0.05 to 3.0% by mass in the clear ink composition of the present invention. If the blending amount is less than 0.05% by mass, the stability against heat can not be improved and the storage stability is lowered, and microgels are likely to be generated. When the blending amount exceeds 5.0% by mass, the result of the self weight filtration test and the result of the accelerated test thereof are inferior.

Further, even if the average particle diameter is less than 1 nm, further improvement in stability against heat can not be expected, and it is also difficult to produce such an inorganic filler having a very fine particle size.

On the other hand, when the average particle diameter exceeds 200 nm, it is difficult to uniformly disperse the ink composition in the ink composition, and the stability against heat can not be improved, resulting in poor storage stability and microgels. Also, the result of the acceleration test of the self weight filtration test is poor.

In view of the fact that the ink composition of the present invention is a clear ink, the kind of the inorganic filler to be added and the blending amount thereof are preferably not less than 30%, preferably not less than 50%, more preferably not less than 70% To be more than 90%.

(Pigment dispersant)

In addition, the clear ink composition for photocurable inkjet printing of the present invention may contain a pigment dispersant if necessary.

The pigment dispersant is used to improve the dispersibility of the pigment and the storage stability of the ink composition for photocurable inkjet printing of the present invention. Any conventionally used pigment may be used without particular limitation, and a polymer dispersant is preferably used. Examples of such pigment dispersants include carbodiimide dispersants, polyester amine dispersants, fatty acid amine dispersants, modified polyacrylate dispersants, modified polyurethane dispersants, multi-chain type polymeric nonionic dispersants, and polymeric ion activators . These pigment dispersants may be used alone or in combination of two or more.

The pigment dispersant is preferably contained in an amount of 1 to 200 parts by mass based on 100 parts by mass of the total pigment to be used. When the content of the pigment dispersant is less than 1 part by mass, the pigment dispersibility and the storage stability of the ink composition of the present invention may be deteriorated. On the other hand, it may be contained in an amount exceeding 200 parts by mass, but there may be no difference in effect. A more preferable lower limit of the content of the pigment dispersant is 5 parts by mass, and a more preferable upper limit is 60 parts by mass.

(Ketone resin)

The ink composition for photocurable inkjet printing of the present invention may contain a ketone resin in order to prevent stickiness.

The ketone resin is not particularly limited as long as it is soluble in the above-mentioned photopolymerizable compound, and a known ketone resin can be used.

The ketone resin is preferably a ketone resin having a hydroxyl group. Specific examples thereof include (1) ketone group-containing compounds such as aromatic ketone compounds such as acetophenone and alicyclic ketone compounds such as cyclohexanone and trimethylcyclohexanone And an aldehyde compound such as formaldehyde; (2) a ketone resin having a substituent capable of reacting with an isocyanate compound, and a polyisocyanate compound such as isophorone diisocyanate And a hydroxyl group-containing urethane-modified ketone resin obtained by reacting. These may be used alone or in combination of two or more.

These ketone resins are commercially available. Specific examples thereof include SK and PZZ-1201 manufactured by Evoniks.

When the ketone resin is contained, the content of the ketone resin in the ink composition for photo-curable inkjet printing is preferably 5.0 to 15.0 mass% in order to prevent stickiness from occurring.

The clear ink composition of the present invention can be prepared by a conventionally known method. For example, the clear ink composition can be prepared, for example, by mixing and stirring the above-mentioned respective components and any of the following optional components. The viscosity of the obtained clear ink composition at 25 캜 is adjusted to 1.0 mPa s or more. The viscosity of the clear ink composition at 25 캜 is 10.0 mPa s or less, preferably 5.0 mPa 쨌 s or less. Such a clear ink composition has excellent ejection stability when printed by an inkjet recording apparatus. In particular, such a clear ink composition is excellent in discharge stability at room temperature from the head of an inkjet recording apparatus designed for low viscosity ink for energy saving, high speed, and high definition.

The clear ink composition of the present embodiment can be printed and cured by a conventionally known method. For example, the clear ink composition can be obtained by exposing the clear ink composition onto a substrate or a printed matter printed on the substrate (hereinafter simply referred to as a substrate or the like) and then exposing the coating film of the clear ink composition, And can be printed and cured by the method of making.

As the substrate, those conventionally used in a clear ink composition for UV-LED curable inkjet printing are used without any particular limitation. Specific examples thereof include paper, a plastic film, a capsule, a metal foil and glass. Of these, vinyl chloride, polycarbonate and the like which are used as a bottom material are preferable.

The clear ink composition of the present embodiment is supplied to, for example, a printer head corresponding to a low viscosity of an inkjet recording apparatus (inkjet printer), and is ejected from the printhead to the substrate. The discharged clear ink composition is deposited on the substrate so that the film thickness is, for example, 1 to 60 mu m. The deposited clear ink composition is suitably cured by irradiation with UV-LED. As the ink jet recording apparatus for printing the clear ink composition of the present embodiment, a conventionally known ink jet recording apparatus is used. At this time, when a continuous type ink jet recording apparatus is used, it is preferable that the clear ink composition is further added with a conductivity imparting agent so that the conductivity is appropriately controlled.

&Lt; Optional components of clear ink composition &gt;

Next, arbitrary components suitably included in the clear ink composition of the present embodiment will be described. In the clear ink composition of the present embodiment, in addition to the above-described components, optional components may be appropriately blended to express various functions. For example, the clear ink composition may contain a pigment such as a surfactant, a solvent, a dye and other colored pigments, a sensitizer, a pigment dispersant, and various additives.

(Surfactants)

The surfactant may be appropriately compounded in order to improve the discharge stability and the like of the clear ink composition according to the head of the ink jet recording apparatus in which the clear ink composition is used. As the surfactant, a silicone surfactant conventionally used suitably for an ink composition for photocurable inkjet printing is exemplified. Specifically, examples of the silicone surfactant include a polyether-modified silicone oil, a polyester-modified polydimethylsiloxane, and a polyester-modified methylalkylpolysiloxane. These surfactants may be used in combination.

The content of the surfactant is preferably 0.005 mass% or more in the clear ink composition. The content of the surfactant is preferably 1.0% by mass or less in the clear ink composition. When the content of the surfactant is less than 0.005% by mass, the clear ink composition tends to have a large surface tension, and thus the discharge stability tends to deteriorate. On the other hand, when the content of the surfactant is more than 1.0% by mass, the clear ink composition tends to contain bubbles, which tends to lower the discharge stability.

(solvent)

The solvent may be appropriately blended in the clear ink composition. Examples of the solvent include an ester organic solvent, an ether organic solvent, an ether ester organic solvent, a ketone organic solvent, an aromatic hydrocarbon solvent, a nitrogen-containing organic solvent and the like. As the solvent, the boiling point at normal pressure (1.013 x 10 ² kPa) is 150 to 220 ° C.

It is preferable that the organic solvent is not maximally used from the viewpoints of the curability of the clear ink composition, environmental problems, and the like. Therefore, the content of the organic solvent in the clear ink composition is preferably 5% by mass or less, more preferably 2% by mass or less, and further preferably not used.

(Other pigment)

A pigment other than an inorganic filler having an average particle diameter of 1 to 200 nm may be appropriately blended to obtain a clear ink composition of each color. Such a pigment is conventionally used in conventional ink compositions for photocurable ink-jet printing, specifically, an organic pigment or an inorganic filler that is well dispersed in a clear ink composition and has excellent weather resistance is preferable. Specific examples of the organic pigments include organic pigments such as dye lake colors, azo pigments, benzimidazolone pigments, phthalocyanine pigments, quinacridone pigments, anthraquinone pigments, dioxazine pigments, indigo pigments, thioindigo pigments, perylene pigments, perinone pigments, A pyrrolone-based pigment, an isoindolinone-based pigment, a nitro-based pigment, a nitrone pigment, a flavanthrone pigment, a quinophthalone pigment, a pyranthrone pigment and an indanthrone pigment. These pigments may be used in combination.

However, when these pigments are blended, it is necessary not to interfere with the effect of blending the inorganic filler having an average particle diameter of 1 to 200 nm.

(Sensitizer)

The clear ink composition for photocurable inkjet printing of the present invention further has a light absorbing property at a wavelength range of ultraviolet light of 400 nm or more in order to promote curability against ultraviolet rays using a light emitting diode (LED) as a light source, (Compound) in which the function of increasing and decreasing the curing reaction is expressed by the light of the wavelength of the light-sensitive agent can be used in combination.

Further, the expression &quot; a sensitizing function is expressed by light having a wavelength of 400 nm or more &quot; means that the light absorbing property is exhibited in a wavelength region of 400 nm or more. By using such a sensitizer, the LED curing property of the clear ink composition for photocurable inkjet printing of the present invention can be promoted.

As the photosensitizer, an anthracene-based sensitizer, a thioxanthone-based sensitizer, and the like, preferably a thioxanthone sensitizer. These may be used alone or in combination of two or more.

Specific examples thereof include anthracene type sensitizers such as 9,10-dibutoxyanthracene, 9,10-diethoxyanthracene, 9,10-dipropoxyanthracene and 9,10-bis (2-ethylhexyloxy) And thioxanthone sensitizers such as 2,4-diethylthioxanthone, 2-isopropylthioxanthone and 4-isopropylthioxanthone. Representative examples of commercially available products include DBA and DEA (manufactured by Kawasaki Chemical Industry Co., Ltd.) as anthracene-based sensitizers, and DETX and ITX (manufactured by LAMBSON) as thioxanthone sensitizers. However, it is better not to use thioxanthone sensitizer to prevent discoloration.

(Various additives)

As the various additives, a thermosetting resin, a photostabilizer, a surface treatment agent, a viscosity reducing agent, an antioxidant, an antioxidant, a crosslinking accelerator, a polymerization inhibitor, a plasticizer, a preservative, a pH adjuster, a defoaming agent and a humectant may be appropriately mixed.

As described above, the clear ink composition of the present embodiment contains 40 to 90 mass% monofunctional monomer, 15 to 50 mass% polyfunctional monomer, and 5 to 15 mass% acylphosphine-based photopolymerization initiator. This clear ink composition is excellent in UV-LED curing property.

Further, the resulting cured coating film is excellent in adhesion and scratch resistance to a substrate.

Example

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, "%" means "mass%" and "part" means "mass part".

The materials used in the following examples and comparative examples are as follows.

<Pigment dispersant>

Agisper (registered trademark) PB821 (manufactured by Ajinomoto Fine Techno Co., Ltd.)

&Lt; Photopolymerizable compound &gt;

Benzyl acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd.)

Vinyl caprolactam 1,6-hexanediol diacrylate

<Photopolymerization initiator>

TPO: 2,4,6-trimethylbenzoyl diphenyl phosphine oxide (manufactured by Lamberti)

<Additives>

BYK-315 (silicone additive, manufactured by BYK Chemie)

UV-5 = dioctyl maleate (manufactured by Chroma Chemical)

UV-22 = quinone polymerization inhibitor (manufactured by Chroma Chemical Co.)

<Inorganic Oxide>

Silica (particle diameter 20 nm, NANOCRYL C 140, manufactured by Evonik, dispersed in 1,6-hexanediol diacrylate, solid content 50%),

Aluminum oxide (particle diameter 80 nm, AEROXIDE Alu-C, Japan Aerosil, self dispersion, solid content 10%)

<Preparation of Aluminum Oxide Dispersion>

10 parts by mass of AEROXIDE Alu-C, 1 part by mass of PB-821 as a dispersing agent, and 89 parts by mass of benzyl acrylate were pulverized for 60 minutes with Redi mill (bead diameter: 0.2 nm, packing rate 50%) to obtain a viscosity of 4.9 cps, A 10% solid aluminum oxide dispersion of 80 nm was obtained.

&Lt; Examples 1 to 8 and Comparative Examples 1 to 3 &gt;

[Preparation of clear ink composition for photocurable inkjet printing]

Each component was compounded so as to have a composition (mass%) shown in Table 1 and stirred and mixed to obtain a clear ink composition for photocurable inkjet printing of Examples 1 to 8 and Comparative Examples 1 to 3.

[Viscosity measurement of clear ink composition for photocurable inkjet printing]

Each of the clear ink compositions for photo-curable inkjet printing obtained in Examples 1 to 8 and Comparative Examples 1 to 3 was evaluated for viscosity at 25 占 폚 by using an E-type viscometer (trade name: RE100L type viscometer, The viscosity was measured under the condition of 50 rpm.

The viscosity of the clear ink composition for photocurable inkjet printing of Examples 1 to 8 and Comparative Examples 1 to 3 was about 7 mPa · s.

<Visible light transmittance>

Visible light transmittance was measured by an ultraviolet / visible spectrophotometer (trade name: UV-Vis Recording Spectrophotometer, manufactured by Shimadzu Corporation).

<Self weight filtration test>

(Initial) and 60 占 폚 for one month after the preparation of the clear ink composition for photocurable inkjet printing of Examples 1 to 8 and Comparative Examples 1 to 3, 40 g of each clear ink composition for photo-curable inkjet printing was applied to an SPC filter holder , Manufactured by Shibata Scientific Co., Ltd.) using 2600 mesh to measure the degree of penetration.

According to Examples 1 to 8 according to the present invention, despite the clear ink having a high visible light transmittance, even after one month of promotion (storage) at 60 DEG C, the ink has substantially the same storage stability as compared with the initial state immediately after production have. On the other hand, according to Comparative Example 1 in which the content of the inorganic filler was insufficient, Comparative Example 2 in which excess amount of inorganic filler was added, and Comparative Example 3 in which inorganic filler having a large average particle size was added, When the inorganic filler was excessively added or the inorganic filler was too large, the storage stability was already poor immediately after the production.

Claims (6)

A photopolymerizable compound, a photopolymerization initiator, and 0.05 to 5.0% by mass of an inorganic filler having an average particle diameter of 1 to 200 nm in the composition, and a visible light transmittance of 30% or more. The method according to claim 1,
Wherein the inorganic filler is silica and / or aluminum oxide. 3. The method according to claim 1 or 2,
A clear ink composition for photocurable inkjet printing comprising a pigment dispersant having an amino group and / or an acid group. 4. The method according to any one of claims 1 to 3,
A clear ink composition for photocurable inkjet printing comprising a photopolymerizable compound in a total amount of monofunctional monomer having amide group and benzyl acrylate in a clear ink composition for photocurable inkjet printing. 5. The method according to any one of claims 1 to 4,
Wherein the monofunctional monomer having an amide group is N-vinylcaprolactam and / or acryloylmorpholine. 6. The method according to any one of claims 1 to 5,
Wherein the viscosity at 25 占 폚 is 10 mPa 占 퐏 or less.